Final answer:
The weakest linkage between activity and cost driver is (c) lighting on shop floor and number of kilowatt-hours.
Step-by-step explanation:
The linkage between activity and cost driver refers to how closely the cost driver is related to the activity being measured. In this case, we are trying to determine the weakest linkage between activity and cost driver. Looking at the options provided, the weakest linkage would be lighting on shop floor and number of kilowatt-hours. The cost of lighting on the shop floor is not directly dependent on the number of kilowatt-hours consumed, as there could be other factors like energy-saving technologies or natural lighting that affect the cost.